bottom-up 
adjective
Proceeding from the bottom or beginning of a hierarchy or process upwards; non-hierarchical: bottom-up decisions...
- But then the Board was set up to be at the apex of a consensus based bottom-up policy process, which is currently being stifled through an unrepresentative structure.
- In technology the bottom-up open-source software movement is putting new pressure on Microsoft and database giant Oracle.
- The bottom-up approach starts by detailing the metadata ‘facets’ used to describe content items.